With development of display technologies, display screens or touch screens have been widely used in people's lives. Among them, liquid crystal displays (LCDs) have characteristics of small volume, low power consumption, no radiation and the like, and are of great significance in the market. Organic light-emitting diodes (OLEDs) have advantages of self-luminescence, rapid response, wide view angle, high luminance, vivid color, light weight and thin thickness, and the like, and also have been widely applied in the market.